As we come to the end of a series and decide we would like to watch it over from the very beginning it would be nice if there was an easy way to accomplish that task. I haven’t found one yet.
Going through 10 seasons of 12 to 24 episodes per season and doing them one by one is painful.
Go to the show itself. On most Remote-controlled apps (TV), you long press [SELECT] on any episode to get a small menu, and there should be a button to [Go to Show]. Here, select to [Mark as Unwatched].
If this button is gone, and instead you have a [Mark as Watched] button, this is because you have not watched all media in the show. If you wish to reset all episodes, select to mark the show as [Watched], then the button should change and allow you to [Mark as Unwatched].